Nauru's leaders are mocking New Zealand's efforts to engage with them, a lawyer for a Nauru MP says.
David Lambourne is one of a number of lawyers who have been blocked from entering Nauru to represent opposition MP Roland Kun, who has had his passport cancelled by Justice Minister David Adeang.
Mr Kun had his passport cancelled in June, despite not being charged for any crime.
His wife, who lives in New Zealand with their three young children, had earlier been banned from Nauru.
New Zealand announced it was withholding its aid funds to the Nauru Justice Ministry this year, prompting a rebuke from Nauru President Baron Waqa that New Zealand was misinformed and bullying the tiny island.
Mr Lambourne said there should be stronger international reaction.
"Certainly I've seen the way in which President Waqa and Minister Adeang mocked the New Zealand government and the New Zealand government's attempts to try and discuss their concerns with Nauru.
"President Waqa and Minister Adeang think this is a joke, and really countries like Australia should be joining New Zealand in its expression of concern about the complete erosion of the rule of law in Nauru."
Nauru was benefiting financially from Australia's asylum seeker detention centre in Nauru and didn't miss New Zealand's funding, he said.
The country's rule of law had totally broken down, Mr Lambourne said.
He said Mr Adeang had a personal vendetta against his client that he was executing at will and there was no chance his client would be able to reach his family for Christmas.
"This is all part of the game that Minister Adeang in Nauru is playing. As far as I can work out, his whole objective is to try and make life as difficult as possible for his political opponents.
"And so he is using every legal means he can to try and disrupt their lives and cause as much grief as possible."
Mr Adeang was employing delay tactics as he knew he was wrong to cancel the passport, Mr Lambourne said.